The aim of my PhD thesis is to identify and understand the processes that shaped the remarkable biodiversity of the
Mediterranean Basin. To achieve the objectives I have used as model organisms the spider genera Harpactocrates and Parachtes, which are endemic from the Western Mediterranean. The results obtained so far are based on the information provided by molecular data and using phylogenetic inferences, divergences time estimations and opulation genetic approaches. At the moment, I have reached the following conclusions: 1) the pattern and timing of species formation in the spider genus Parachtes match the geochronological sequence of the opening of the western Mediterranean Basin, 2) Hapractocrates colonized the Alps from the Iberian Peninsula, 3) divergence times of the genus Hacrpactocrates predate glaciations, ruling out the Pleistocene speciation hypotheses, 4) pleistocene glacial cycles played a main role in structuring populations of the pyrenean species Harapctocrates ravastellus, and glacial refugias were identified along the Pyrenees, 5) the phylogeographic pattern of the 3 species from the Iberian Central System (H. gredensis, H. globifer y H. gurdus) reveal deep population structure dating around the Plio-Pleistocene, suggesting the existence of several refugias in the Central System.